Explaining HIV Statistics

Jun 13, 2011

Hello, Dr. Bob. I hope all is well with you.

I was just reading a question to you from Jake from Down Under. You said the CDC puts the risk of transmission from receptive anal sex with someone known to be poz at 5 in 1,000 exposures. I should disclose that I flunked statistics. For someone who ain't all that smart in them there statistics, that doesn't seem like a high risk. To me, it would seem I would have had a better chance of winning the lottery. Well, not quite.

I became poz after having receptive anal sex with a friend of 10 years. He took the condom off without me knowing. I know, many roll their eyes at that, but it is hard to tell whether it is still on--especially in the dark. If I had it to do over again, I would obviously make damn sure it stayed on. I hadn't bottomed that much. I've read HIV is actually a hard virus to transmit. Everything has to be just right, or wrong. I have wondered whether my lack of previous bottoming experience made infection that more likely. But, I digress and not suggesting bottoms just need more experience to prevent infection. That would be stupid.

Anyway, is 5 in 1,000 considered to be a high risk, moderate risk, or low risk? I bet it is considered a high risk. I'm asking, because I'm sure there are others like me, not great at statistics, who would tell themselves that isn't much risk when they read that. I think it would be helpful to put it in percentages--such as, you would have a 80% chance of infection. Or, something like that. I know the best advice to people is to never have unprotected sex. But, we know people don't always do that. I think there are people who just don't care. But, there are people who think it just isn't going to happen to them. I know I looked at the 1 million number poz in the U.S. and thought the chances of me getting infected would be small--especially using condoms. I felt the chances of me having sex with one of those 1 million would be low in a country of over 300 million. And, I would have never thought it would come from a longtime friend. I wasn't taking into account that many of those 1 million infections here are in the gay community making the chances that much higher. I've read 1 in 5 gays are positive.

Response from Dr. Frascino

Hi.

The CDC's estimated statistics for acquiring HIV are meant to give a sense of the relative risk of acquiring the virus via various types of sexual activity. They are not meant to define the actual risk of any one single sexual coupling. There are many variables involved in whether HIV transmission occurs, including both the virus (viral strain, viral load, etc.) and the host (host immune integrity, concurrent STDs, local trauma, etc.) Unprotected receptive anal sex is the riskiest (by far) activity. Even though the statistic might seem reassuring, your experience is a perfect example of the unfortunate reality associated with this risk. Yes, HIV is "hard to transmit" compared to, say, the common cold or flu, which can be transmitted through the air via a cough or sneeze. It's also much easier to transmit other STDs, such as syphilis, gonorrhea, chlamydia, herpes, etc. Compared to HIV. However, that doesn't mean HIV is not a clear and present danger. There have been over 60,000,000 of us who have acquired the virus. Despite knowing how to prevent HIV, we still have 7,000 new infections per day worldwide. Even in the U.S., new infection rates have remained constant over recent years at 56,000 per year. That's one new infection in the U.S. every nine minutes.

Review the chapter on HIV statistics in the archives for a more detailed discussion. I'll repost below a link that provides an example of what can be found in the archives.

Finally, you are absolutely correct: "the best advice is to never have unprotected sex"!

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